Cardiovascular disease (CVD) is the leading killer of patients with rheumatoid arthritis (RA) who have a 2-3 fold increased risk of myocardial infarction compared to members of the general population. Traditional cardiovascular (CV) risk factors alone do not accurately predict CVD in RA patients and therefore adequate primary prevention strategies are lacking. Systemic inflammation from active RA is strongly associated with CV risk in RA patients, but mechanisms by which inflammation increases CV morbidity and mortality are poorly understood. High density lipoprotein (HDL) is an anti-atherogenic molecule that regulates systemic inflammation by promoting cholesterol efflux and preventing oxidation of low density lipoproteins (LDL). We have previously demonstrated that HDL function is impaired and significantly associated with both disease activity and systemic inflammation, in patients with RA. We further showed that active RA leads to oxidative and protein changes in HDL resulting in dysfunctional HDL. Oxidized low density lipoproteins (ox-LDL) have been directly implicated in the pathogenesis of RA through signaling via the lectin-like ox-LDL receptor 1 (LOX- 1) in the joint synovium. Our preliminary results suggest that modulation of HDL function by increasing HDL's ability to prevent oxidation of LDL is associated with improvement in arthritis activity. We hypothesize that modulation of HDL function represents a novel pathway through which to both decrease arthritis activity and improve CV risk in patients with RA. We will test our hypothesis under two specific aims. In aim 1, we will evaluate whether modulation of HDL function using HDL mimetic peptides can reduce atherosclerosis and joint inflammation in a recently established mouse model of RA. We will also modulate HDL function by paraoxonase 1 (PON1) gene deletion and overexpression to evaluate the effects on arthritis activity and atherosclerosis in this model. In aim 2, we will determine whether abnormal HDL function contributes to increased CV risk in a carefully characterized, prospective cohort of over 200 RA patients using in vitro assays of HDL function and targeted HDL proteomics and lipidomics. CV risk will be assessed by the progression of carotid atherosclerosis over three year follow-up and by carotid plaque inflammation using positron emission tomography with fluorodeoxyglucose (FDG-PET). The results of this work may identify important mechanisms through which inflammation increases CV risk in RA patients, and thereby determine new markers for risk assessment and specific targets for intervention.